\[x^{2} + px + 56 = 0;\ \ x_{1} = - 4\]
\[x_{1} + x_{2} = - p;\ \ \]
\[x_{1} \cdot x_{2} = 56\]
\[- 4 \cdot x_{2} = 56\]
\[x_{2} = 56\ :( - 4) = - 14.\]
\[- p = - 4 + ( - 14) = - 18\]
\[p = 18.\]
\[Ответ:x_{2} = - 14;p = 18.\]